The present invention relates to flow measuring devices, and particularly to such devices for use with highly viscous lubricants.
Flow detecting or measuring devices are particularly important for lubrication systems as such devices confirm that sufficient lubrication has in fact been dispensed to critical system components. Such flow measuring devices typically include a housing containing a passage for carrying a portion of the flow to be measured and a detection/measurement component or assembly for detecting, or actually measuring, the flow through the passage. Previous measuring devices have used components such as thermistors, transducers, induction sensors or other complex electronic devices to detect or measure flow and often required specialized equipment, such as a customized controller, to receive and evaluate the information from the particular measuring unit. These known measuring devices are generally relatively expensive and often inadequately robust to operate in the temperature extremes often experienced by many lubrication systems and to measure small amounts of lubricant flow.
Further, previous flow detecting or measuring devices typically utilize two oval shaped gears arranged to rotate in a chamber through which a medium to be measured is passed. The flow rate is calculated from the number of revolutions of the gears. Because of the progressive shape of the cavity between the wall and the gears as the gears rotate, one rotational motion of the gears is not proportional to the flow rate. These known devices require several rotations to properly configure the device, and the resulting flow rate output must be extrapolated based upon the results of the configuration instead of being directly determined.